The general class of phosphazene polymers has been known for some time. Etheric polyphosphazenes, i.e., polyphosphazenes containing monoethoxy and/or polyetheroxy substituents have been found to be useful in various applications including, for example, membranes, polymeric electrolytes, biomedical materials, moldings and coatings. Etheric polyphosphazenes have been described by Allcock et al, U.S. Pat. No. 3,370,020; Frank-Filipasio et al, U.S. Pat. No. 3,986,882; Schulz et al, U.S. Pat. No. 4,258,173; Nakacho et al, U.S. Pat. No. 4,840,856; Allcock et al, Macromolecules, Vol. 19, No. 6, 1986, pp. 1508-1512; Tonge et al, J. Electrochem. Soc., January 1987, pp. 269-270; and Abraham et al., J. Electrochem. Soc., December 1989, pp. 3576-3581.
Non-miscible blends of various polyphosphazenes are known and have been described, for example, by Dieck et al, U.S. Pat. No. 4,073,825, Witmer et al, U.S. Pat. No. 4,000,166, Bohm, U.S. Pat. No. 4,559,117 (phosphazene-siloxane blends); Dieck et al, U.S. Pat. No. 4,061,606 (phosphazene-organic polymer blends); Brackenridge, U.S. Pat. No. 4,079,035 (aryloxy phosphazenes as flame retardants for organic polymers) and Tatemoto, U.S. Pat. No. 4,266,698 (crosslinkable blends of iodine containing fluoroelastomers and fluorophosphazenes). Such physical blends are not transparent and exhibit two glass transition temperatures.
Miscible blends within the same class of polyphosphazenes have been described by Connelly et al, J. Applied Polymer Science, 1976, 20, 473 (poly(fluoroalkyloxyphosphazenes)) and by Dieck et al, U.S. Pat. No. 4,055,520, U.S. Pat. No. 4,073,824, J. Applied Polymer Science, 1976, 20, 473 and Beres et al, Macromolecules, 1979, 12, 566 (poly(aryloxy phosphazenes)). However, these systems are limited to mixtures within the same family of poly(phosphazenes), i.e., poly(fluoroalkoxyphosphazenes) with other poly(fluoroalkoxyphosphazenes) or poly(aryloxyphosphazenes) with other poly(aryloxyphosphazenes).
"Miscibility" refers to blends or compositions of polymers in which the component polymers do not undergo phase separation, thus helping to avoid stratification of the components during or after processing. "Miscibility" is a great significance for an admixture of different resins because it ensures homogeneity, and a unity of properties, which greatly facilitates subsequent processing and use of the composition. For example, such blends tend to be transparent, possess a single glass transition temperature, and exhibit other characteristics of a single material. Incompatible physical blends separate into phases containing predominantly their own separate components, and thus may be considered to be immiscible. This characteristic, combined with the often low physical attractive forces across the phase boundaries, usually causes immiscible blend systems to be opaque and suffer from delamination at the phase boundaries, thus preventing the preparation of polymer blends useful for a number of applications.
It has been desired to provide molecularly miscible blends of polyphosphazenes with other classes of polymers. Even though a variety of polyphosphazenes and polyphosphazene-containing blends have been known, prior to this invention applicants were not aware of any miscible blends containing polyphosphazenes with other classes of polymers.